How does Query.prototype.catch() work in Mongoose ?

Last Updated : 16 Nov, 2021

The Query.prototype.catch() function executes the query and returns a promise which can be resolved with either the doc(s) or rejected with the error.
Syntax:

Query.prototype.catch()

Parameters: This function has one parameter i.e. a reject callback function.
Return Value: This function returns a promise.

Installing mongoose :

npm install mongoose

After installing the mongoose module, you can check your mongoose version in command prompt using the command.

npm mongoose --version

After that, you can just create a folder and add a file for example, index.js as shown below.

Database: The sample database used here is shown below:

Example 1:

index.js

const mongoose = require('mongoose'); 
  
// Database connection 
mongoose.connect('mongodb://127.0.0.1:27017/geeksforgeeks', { 
    useNewUrlParser: true, 
    useCreateIndex: true, 
    useUnifiedTopology: true
}); 
  
// User model 
const User = mongoose.model('User', {  
    name: { type: String }, 
    age: { type: Number } 
}); 
  
const promise = User.find({age:"Not a number"});  
  
promise.catch(function(error) { 
    console.log("Error Occurred:", error.message) 
}) 

The project structure will look like this:

Run index.js file using below command:

node index.js

Output:

Error Occurred: Cast to Number failed for value 
"Not a number" at path "age" for model "User"

Example 2:

index.js

const express = require('express'); 
const mongoose = require('mongoose'); 
const app = express(); 
  
// Database connection 
mongoose.connect('mongodb://127.0.0.1:27017/geeksforgeeks', { 
    useNewUrlParser: true, 
    useCreateIndex: true, 
    useUnifiedTopology: true
}); 
  
// User model 
const User = mongoose.model('User', {  
    name: { type: String }, 
    age: { type: Number } 
}); 
  
const promise = User.find({ age: "Not a number" });  
  
promise.catch(function(error) { 
    console.log("Error Occurred:", error.message) 
}) 
  
app.listen(3000, function(error ) { 
    if(error) console.log(error) 
    console.log("Server listening on PORT 3000") 
}) 

The project structure will look like this:

Run index.js file using below command:

node index.js

Output:

Server listening on PORT 3000
Error Occurred: Cast to Number failed for value 
"Not a number" at path "age" for model "User"

Reference:https://mongoosejs.com/docs/api/query.html#query_Query-catch

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